1. Field of the Invention
The present invention relates to a rotor of an electric rotating machine mounted on an electric vehicle or a hybrid vehicle to be used as a motor or an alternator.
2. Description of Related Art
Japanese Patent Application Laid-open No. 2007-236019 describes a rotor of a vehicle-mounted electric rotating machine, including a rotor core fixed to a rotating shaft and formed with magnet accommodating holes, magnets accommodated in the magnet accommodating holes, a filling portion made of resin and filled in each magnet accommodating hole, a first end plate fixed to the rotating shaft at the side of one axial end of the rotor core, and a second end plate fixed to the rotating shaft at the side of the other axial end of the rotor core, the fixing force of the second end plate against the rotating shaft being weaker than that of the first end plate.
The first end plate is in direct contact with the magnets, while on the other hand, the filling portion is interposed between the second end plate and each of the magnets. Since the first end plate is in direct contact with the magnets, the heat generated while the rotor rotates can be dissipated to the outside.
However, since the linear expansion coefficient of the filling portion made of resin is larger than that of the rotor core and magnets, the filling portions expand and press the second end plate while the rotor rotates and generates heat. As a result, the second end plate departs from the rotor core, causing the fixing force of the second endplate against the rotating shaft to decrease. Hence, the fixing force of the second end plate against the rotating shaft which is initially lower than that of the first end plate further decreases.